Seal for track pins and the like

ABSTRACT

A seal assembly for use in excluding mud, dirt and the like from an interior space defined by two relatively movable machine elements, comprising a resilient sealing ring having one outwardly facing mounting surface for reception in a machine bore, and a second axially directed end face sealing surface for engaging an oppositely directed, cooperating face of a machine element in a sealing relation. The mounting surface and the sealing surface are axially offset from each other and joined by an at least partially frustoconical body portion so that axially applied thrust tends to deform the seal ring, which is held against axial movement, either radially inwardly or outwardly. A relatively stiff support ring extends around an inner portion of the seal body to prevent inward radial deformation upon the application of the compressive radial loads, so that an end loading force creates a tight seal between the seal ring and the bore. Preferably, the seal body is formed with a recess or reentrant which permits removable reception of the ring therein prior to assembling the elements to apply the axially directed load between an end sealing face on the seal body and a corresponding face on one machine element.

United States Patent [72] lnventor Seymour A. Hatch Oak Park, 111.

[21] Appl. No. 819,042

[22] Filed Apr. 24, 1969 [45] Patented [73] Assignee Nov. 23, 1971Chicago Rawhide Manufacturing Company Chicago. Ill.

I54] SEAL FOR TRACK PINS AND THE LIKE 2,687,909 8/1954 Blackman etal.

ABSTRACT: A seal assembly for use in excluding mud, din and the likefrom an interior space defined by two relatively movable machineelements, comprising a resilient sealing ring having one outwardlyfacing mounting surface for reception in a machine bore, and a secondaxially directed end face sealing surface for engaging an oppositelydirected. cooperating face ofa machine element in a sealing relation.The mounting surface and the sealing surface are axially offset fromeach other and joined by an at least partially frustoconical bodyportion so that axially applied thrust tends to deform the seal ring,which is held against axial movement, either radially inwardly oroutwardly. A relatively stiff support ring extends around an innerportion of the seal body to prevent inward radial deformation upon theapplication of the compressive radial loads, so that an end loadingforce creates a tight seal between the seal ring and the bore,Preferably. the seal body is formed with a recess or reentrant whichpermits removable reception of the ring therein prior to assembling theelements to apply the axially directed load between an end sealing faceon the seal body and a corresponding face on one machine element.

PATENTEDN 23 3.622.165

IN VE NTOR SEYMOUR A. HATCH SEAL FOR TRACK PINS AND THE LIKE BACKGROUNDOF THE INVENTION The present invention relates generally to seal units,and also to combination machine assemblies which include such sealunits, and is particularly directed to so-called end face seals for usewith machine elements having two relatively movable parts which undergorotary or oscillatory motion with respect to each other. Seals of thetype with which the present invention is concerned are intended toexclude dirt, sand, mud, and the like from the machine assembly, and toretain a supply of lubricant inside a desired portion of such machineassembly. In particular, a seal of the type with which the presentinvention is concerned is retained within a portion of one machinemember and held against movement therein, while presenting a sealing endface for sliding, sealing engagement with a corresponding end face of asecond machine member which undergoes relative motion while the twosealing faces thus presented are in engagement with each other.

The seal of the present invention is particularly useful in sealingtrack pin assemblies, a plurality of which make up a crawler trackassembly or crawler chain used to propel a crawler-type tractor or othertrack-laying vehicle, and are also adapted to be used with the trackrollers which support a crawler track assembly comprised of a series ofpins, links, plates, and the like.

A seal of the type with which this invention is concerned is called uponto resist abrasion from sand, grit, and the like, and to permit relativemotion between a pair of machine elements while maintaining an axiallydirected load or force on one of the elements to maintain the seal, evenduring a certain amount of operational misalignment thereof, so that thesealing effectiveness of the unit may be maintained even whenmisalignment of track links or the like occurs in use.

Improved materials used in the seal manufacturing industry have now madepossible the production of seal units which have a life expectancy whichis substantially the same as or greater than that of the other machinecomponents desired to be sealed, that is, in normal, use seals may beexpected to last the lifetime of their associated components, such astrack pins or track rollers, so that the seals need normally not bereplaced while the other components are still in useable condition.However, several known seals for crawler assemblies having a lifetimecapability are somewhat difficult to install, or have been characterizedby metal-to-metal sealing surfaces which require extremely precisefinishing, honing or lapping operations, or have had other at leastpartially undesirable characteristics. Other known seals have beencharacterized by metal-to-metal contact between the seal flange and themachine member in which they are received, and operate on the principleof torsional deflection in use. These seals often require exactmachining of the members in which the metal portions are received.Furthermore, a torsional deflectiontype seal is obviously notappropriate for use where the relative motion is rotary rather thanoscillatory.

Therefore, an ideal track pin or like seal is one which, in addition tohaving a long life expectancy, is characterized in that it is easy tomanipulate during installation, is of simple design, provides therequisite stiffness against inward radial deflection, provides means forreceiving varying axial forces on the sealing face portion of the seal,provides reasonable flexibility, and presents a sealing face having thecapability of mating with an opposed element to fonn a proper seal therebetween.

Accordingly, an object of the invention is to provide a track pin likeseal which is simple to manufacture and easy to install.

Another object is to provide a seal unit which has means therein forfacilitating reception and retention in a machine element in a freestate, before the seal is compressed to its operating axial dimension inposition of use.

Another object is to provide a seal unit having a resilient seal bodyand a resilient end sealing face portion which affords the primary sealbetween two movable machine elements.

A still further objects is to provide a seal unit including a resilientseal body to which radial stiffness is imparted by insertion of arelatively rigid support member, which serves to support the sealagainst compressive radial loads and direct a portion of the forcesgenerated by such loads along a desired axis.

A further object is to provide a seal having improvedforceversus-deflection characteristics, namely, a seal having a designsuch that strain on the elastomeric body member is primarily in shearrather than in direct compression, thereby permitting greater latitudein material selection and permitting improved sealing performance evenwhen relatively stiff elastomers are used as the primary sealingelement.

A still further object is to provide a seal unit which is easy tomanufacture, which is composed of only two simple components, and whichincludes a homogeneous elastomeric body which may be completelymanufactured before receiving the simple support ring with which it willbe associated in use.

Another object is to provide an end face seal including a resilient bodyportion and means for receiving a stiffener or body supporting elementtherein, and in which the sealing face is axially offset from a surfacewhich serves to mount the seal unit in place within a machine element.

Still another object is to provide a seal unit which comprises a bodyhaving a circumferential mounting surface portion, an axially directedend face sealing portion, a generally frustoconical cross section, and aseal body supporting element in an inner portion of the body to providesupport therefor.

Another object is to provide a machine assembly which includes a sealunit having the foregoing as well as other objects and advantages.

The present invention achieves its objects, and other objects andadvantages inherent therein, by providing a resilient rubber sealingbody with an outer, circumferentially extending mounting surfaceportion, an axially directed end face sealing portion, an offsettingbody portion extending between and joining said portions together, andmeans in said body for receiving a seal body supporting element therein.The exact manner in which this invention achieves these objects andadvantages will become more apparent when the invention is considered inconjunction with the following detailed description of a preferredembodiment thereof, which is shown in the accompanying drawings, whereinlike reference, numerals indicate corresponding parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a exploded perspective viewshowing a portion of a track pin assembly which includes the seal of thethe present invention;

FIG. 2 is a enlarged perspective view, with portions broken away, of aportion of a track link, showing a vertical section through a portion ofthe seal of the invention in position of use thereof;

FIG. 3 is a further enlarged partial vertical sectional view of the sealof the invention in relation to other elements of the track pin and sealassembly;

FIG. 4 is a still further enlarged vertical sectional view of a portionof the seal body of the invention DESCRIPTION OF THE PREFERREDEMBODIMENTS OF THE INVENTION Referring now to the drawings in greaterdetail, FIG. 1 shows portions of a track pin and seal assembly 10,including two track pins 12, each having an end face 14, a cylindricalouter surface 16, and bushings 18 received thereover. FIGv 3 shows thateach bushing 18 includes a circumferentially extending radially innersurface portion 20, an end portion 26 on which is slidingly received theend portion 28 of a track link 30, which includes an opening defined byan inner surface 32 therein. The line 30 is press fitted over the endportion 26 of the bushing 18.

Each link 30, in addition to the end portion 28 and the inner surface32, includes an opposite end portion 34, shown with a raised outersurface portion 36, and has an opening 38 defined by a circumferentiallyextending inwardly facing surface 42, into which is press fitted, in anonrotatable relation, the outer end portion 44 of the track pin 12. Inuse, the bushing 18 is separated by a diametral working clearance, suchas from about 0.005 to about 0.030 inches from the track pin 12, whileone end 28 of the link 30 is pressed over the bushing 18, and the otherend 34 of the link 30 is press fitted over an end portion 34 of a link30.

The end portion 34 of the link 30 also includes an annular groove 46, asbest seen in FIGS. 3 and 4, and an adjacent inwardly facing end surface48, which abuts the end sealing face 22 of the bushing 18. The sealassembly 50 of the invention is received within the inwardly facing,circumferentially extending surface 60 of the groove 46 in a mannerwhich will now be described.

The seal unit 50 includes a generally frustoconical body portion 52,with an increased diameter mounting ring or barb" 54 disposed on oneaxial end of a circumferentially extending, radially outwardly facingseal body mounting surface portion 56. An axial spacer unit or spacerbump 55 is disposed along a portion of the surface 56 in a generallyopposite relation to the barb 54, for reasons which are further setforth herein. The seal body 52 also includes an axial end face sealingportion 58, and a circumferentially extending, radially inwardly facingseal support receiving means 66, which is concentrically disposed withrelation to the mounting surface 56. This means 66 includes wallportions 62, 64 defining a generally rectangular reentrant in the body54 for reception of seal body supporting means in the form of aseparate, removable metal support ring 68, for adding stiffness againstcompressive radial load to the seal body 52.

A tapered or inclined surface 70 extends between the barb 54 adjacentthe outer surface 56 and the end face seal portion 58 of the body,partially defining the frustoconical shape thereof. A similarly taperedsurface 72 extends inwardly from the spacer bump 55 generally parallelto the surface 70, and define an axial face of the body 52. The body 52defined by the surfaces 56, 70, 72 is therefore generally frustoconicalin cross section in the free or uncompressed state thereof.

In preferred embodiment, the seal body 52 is made of anabrasive-resistant, moderately stiff rubber, such as nitrile rubber, andthe ring 68 is of metal or other material which is relatively stiff inrelation to the body 52 of the seal unit 50. The track links 30 as thetrack pins 12 and the bushings 18 are normally made of a steel material.

When it is desired to install the seal unit of the invention within atrack assembly, a bushing 18 is fitted over a track 12, and a link 30 isfitted over the bushing 18, with the end portion 28 of the link 30 pressfit tightly over the end portion 26 of the bushing 18. Anotheroppositely facing or mirror image link (not shown) is also fitted on theother end of the bushing 18 which is in place over the track pin 12.Preferably, the pin 12 is lubricated prior to this partial assembly.Thereafter another link 30 is selected, and the seal body 52, with thesupport ring 68 in place therein, is placed in the groove 46 andretained in place therein in a relatively unstressed condition, with thebarb 54 engaging the inner surface 60 of the groove 46 to hold the body52 in place. With the seal body 52in a relatively unstressed condition,the outer diameter of the mounting surface 56 is ordinarily somewhatsmaller than the outer diameter of the groove 46, but the barb 54 is ofa slightly greater diameter than the groove 46; therefore, the barb 54serves to hold the seal body 52 in place during assembly. Thereafter,the grease is applied to appropriate surfaces to lubricate the slidingface 58 of the seal 50 and the bearing surfaces of the track link joint.

Next, the end portion 34 of the link 30 is placed over the end portion44 of the track pin 12, with the inner surface 42 of the end portion 34engaging the pin 12 with a tight press fit. The end portion 34 is movedaxially over the pin 12 so as to bring the face portion 48 of the linkend 34 into an abutting or nearly abutting position in relation to theend face 22 of the bushing 18. As assembly is made in this manner, theseal body 52, including the end sealing face portion 58, is compressedaxially, such as to the position shown in FIG. 3, and a portion of thisaxial compressive force causes radial outward expansion of the mountingsurface 56 of the seal body 52, deflecting the barb 54 into the downwardposition, in the plane of the surfaces 56, as shown in FIG. 3. Thus,because of the frustoconical shape of the body 52, a force appliedaxially in compression to the face 58 tends to enlarge the outerdiameter of the seal body 52. The mounting surface 60 acts as arestraint to place the entire seal unit under a desired compressiveforce, and the compressive radial load developed in opposition to thisforce cannot be dissipated inwardly because the presence of the ring 66.Nevertheless, because of the frustoconical shape of the seal assembly50, the sealing surface 58 of the seal body 52 may deflect much more perunit of applied force than would be the case if the body were stressedonly in compression when an axial load is applied thereto. In otherwords, the strain on the body 52 is primarily in shear rather than indirect compression, Thus, a stiffer rubber may be used for purposes ofimproved longevity, without sacrificing the flexibility which ispreferred to avoid criticality in axial dimensional tolerances. Theprovisions of the spacer bump 55 provides a means of spacing the sealassembly 50 apart from an end wall of the groove 46, and preventsbottoming" of the seal 50in the groove 46 under normal loads.

With the seal assembled in this manner, a rubber-to-metal seal isdeveloped which is extremely effective in excluding dirt from theassembly and in retaining lubricant therein for an indefinite time.Because the primary seal surface at the interface of the surfaces 58, 22is a rubber-to-metal seal track pin, misalignment which occurs in use ofthe tracks under extremely heavy loads can be easily accommodated,although alignment is, within limits, maintained by the engagement ofthe face 22 with the oppositely disposed surface 48. A secondary sealexists between the surfaces 56 and 60, but since the axial load tends tomaintain this seal in a tight condition, no relative movement takesplace at this interface.

in a preferred embodiment, the materials referred to above giveexcellent results, however, other suitable materials having the desiredcharacteristics of resilience and stiffness respectively, may besubstituted for the materials illustrated herein.

A seal made as described is relatively easy to manufacture since it iscomposed of only two simple components. The elastomeric body can behomogeneous and its manufacture can be completed before the simplesupport ring is snapped into place.

A seal made as described above may be installed easily and does not callfor special skills, unusual tools or the like. In use, such a seal willlast several million oscillating or rotating cycles, and will normallyhave a life expectancy which is longer than that of the other componentswith which it is associated, such as portions of a track assembly.

it will thus be seen that the present invention provides a new anduseful seal assembly and combination thereof with a crawler trackassembly, both having a number of advantages and characteristics,including those pointed out herein and others which are inherent in theinvention.

lclaim:

l. A sea] unit for excluding foreign matter from the interior of anassembly which includes first and second members which are movablerelative to each other, at least one of said members having an axiallyfacing, radially extending sealing surface, said seal unit comprising,in combination, a seal body formed entirely of an otherwise unsupportedelastomeric material to permit forces applied axially to one portion ofsaid body to be transformed to forces causing radial compressive loadand radial dimensional change and having a generally annularconfiguration and including an axial end face sealing portion disposedin a given plane and having a given radial extent, a radially outer,generally circumferentially extending outwardly facing mounting surfaceportion, a portion of said mounting surface portion being axially ofisetfrom said given plane, a generally frustoconical oiTsetting body portionextending between and joining said mounting surface portion and said endface sealing portion, a radially inner, circumferentially extending bodyportion disposed generally concentrically with said mounting surfaceportion, means in said inner portion of said body for receiving sealbody supporting means, and seal body supporting means associated withsaid means for receiving said supporting means and supporting only saidinner portion of said seal body. Said supporting means being relativelymore rigid than said body, having a substantial axial extent in relationto the axial extent of said mounting surface portion, and being spacedaxially apart from said end face sealing portion of said seal body.

2. A seal unit as defined in claim 1 in which said seal body supportingmeans is a metal ring.

3. A seal unit as defined in claim I in which said means for receivingsaid seal body supporting means comprises a reentrant of rectangularcross section, having a substantial portion thereof disposed radiallyinwardly of said mounting surface portion.

4, A seal unit as defined in claim 1 wherein said seal includes aslightly angled, generally axially facing end portion disposedoppositely from said end face sealing portion and having a substantialradial extent, said portion terminating at its outer edge in an axialspacer for offsetting the remainder of said end portion from means forreceiving said body.

5. A seal unit as defined in claim 1, which further includes a mountingbarb for holding said seal unit in place in the absence of compressiveradial load forces, said barb extending radially outwardly from theplane of said mounting surface portion for engaging an associatedmounting surface on a machine element, said barb being movable to aposition in which a portion of the outer surface thereof lies in theplane of said mounting surface.

6. A seal unit as defined in claim 1 in which said offsetting bodyportion, said end face sealing portion and said mounting surface portionare arranged so that radially inwardly directed forces applied to thecircumference of said mounting surface portion tend to be transmitted tosaid end face sealing portion to urge said portion into a tightersealing relation with an oppositely directed face with which it isassociated in use, and forces applied axially against said end facesealing portion are directed at least partially radially outwardlytoward said mounting surface portion of said unit.

7. A seal unit as defined in claim 2, in which said metal ring isremovably held in place, in use, within said seal body.

8. In combination, a seal unit as defined in claim 1, a first machineelement including an axial end sealing face portion, and a secondmachine element associated with said first element and being mounted formovement relative thereto, said second element having acircumferentially extending, radially inwardly facing mounting surfaceportion thereon, said mounting surface of said seal unit being engagedby said mounting surface portion of said second element, and said endsealing face portion of said seal unit engaging said end sealing faceportion of said first machine element.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,622,165 Dated November 23, 1971 Inventor(s) Seymour A. Hatch It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby correrf as shown below:

Column 1, line +1, the third should be between "use" and"sea ls" insteadof after "normal".

Column 2, line 1, "objects" should be "object".

Column 2,line 7 "line" should be --link--.

Column 3, line &8, insert --as well-- between "30" nd "as" Column line8, the second "the" should be Column 4, line 26, "provisions" should be--provision--.

Signed and sealed this 12th day of September 1972.

(SEAL) Attest:

EDWARD M .FLETCHER,JR. ROBERT COTTSCHALK Attest ing Off i setCommissioner of Patents ORM PO-105O (10-69) uscoMM-Dc seam-peg U 5MIWERNMFNY PRINTING OFFICE 195! 0*356l3

1. A seal unit for excluding foreign matter from the interior of anassembly which includes first and second members which are movablerelative to each other, at least one of said members having an axiallyfacing, radially extending sealing surface, said seal unit comprising,in combination, a seal body formed entirely of an otherwise unsupportedelastomeric material to permit forces applied axially to one portion ofsaid body to be transformed to forces causing radial compressive loadand radial dimensional change and having a generally annularconfiguration and including an axial end face sealing portion disposedin a given plane and having a given radial extent, a radially outer,generally circumferentially extending outwardly facing mounting surfaceportion, a portion of said mounting surface portion being axially offsetfrom said given plane, a generally frustoconical offsetting body portionextending between and joining said mounting surface portion and said endface sealing portion, a radially inner, circumferentially extending bodyportion disposed generally concentrically with said mounting surfaceportion, means in said inner portion of said body for receiving sealbody supporting means, and seal body supporting means associated withsaid means for receiving said supporting means and supporting only saidinner portion of said seal body. Said supporting means being relativelymore rigid than said body, having a substantial axial extent in relationto the axial extent of said mounting surface portion, and being spacedaxially apart from said end face sealing portion of said seal body.
 2. Aseal unit as defined in claim 1 in which said seal body supporting meansis a metal ring.
 3. A seal unit as defined in claim 1 in which saidmeans for receiving said seal body supporting means comprises areentrant of rectangular cross section, having a substantial portionthereof disposed radially inwardly of said mounting surface portion. 4.A seal unit as defined in claim 1 wherein said seal includes a slightlyangled, generally axially facing end portion disposed oppositely fromsaid end face sealing portion and having a substantial radial extent,said portion terminating at its outer edge in an axial spacer foroffseTting the remainder of said end portion from means for receivingsaid body.
 5. A seal unit as defined in claim 1, which further includesa mounting barb for holding said seal unit in place in the absence ofcompressive radial load forces, said barb extending radially outwardlyfrom the plane of said mounting surface portion for engaging anassociated mounting surface on a machine element, said barb beingmovable to a position in which a portion of the outer surface thereoflies in the plane of said mounting surface.
 6. A seal unit as defined inclaim 1 in which said offsetting body portion, said end face sealingportion and said mounting surface portion are arranged so that radiallyinwardly directed forces applied to the circumference of said mountingsurface portion tend to be transmitted to said end face sealing portionto urge said portion into a tighter sealing relation with an oppositelydirected face with which it is associated in use, and forces appliedaxially against said end face sealing portion are directed at leastpartially radially outwardly toward said mounting surface portion ofsaid unit.
 7. A seal unit as defined in claim 2, in which said metalring is removably held in place, in use, within said seal body.
 8. Incombination, a seal unit as defined in claim 1, a first machine elementincluding an axial end sealing face portion, and a second machineelement associated with said first element and being mounted formovement relative thereto, said second element having acircumferentially extending, radially inwardly facing mounting surfaceportion thereon, said mounting surface of said seal unit being engagedby said mounting surface portion of said second element, and said endsealing face portion of said seal unit engaging said end sealing faceportion of said first machine element.